The invention relates to a device for transporting bulk material, in particular for electrodeposition of aluminum from aprotic aluminum-organic electrolytes free of oxygen and water, with a vibrator conveyor. The conveying trough of the vibrator conveyor is arranged spirally around a central pipe and is surrounded by a vessel. Said vessel contains a liquid, into which the vibrator conveyor with the central pipe dips partially.
It is known that by surface improvement of metal parts, whose life can be lengthened, new areas of use can be opened up. For example, coating of light metal and ferrous materials may be appropriate, as they generally involve relatively base metals, whose surfaces may corrode under the influence of the atmosphere. By suitable pretreatment the parts are given a polished surface without cover layer. The metallic coating can be supplemented with an aftertreatment.
During the electrodeposition the pourable small parts must be held together so that each individual part has electric contact. On the other hand, the bulk material to be treated should be spread out to the extent that the metal deposition can occur on a product surface as large as possible and a current density as uniform as possible is ensured on all parts. Another essential prerequisite for obtaining satisfactory metal coatings with a uniform layer thickness is sufficient mixing of the material during the electrodeposition. The devices for electrolytic surface coating are equipped with conveyor means for the transport of the bulk material through the electrolyte, whereby in conjunction with corresponding inlet and outlet locks either continuous or intermittent feeding and removal of the material becomes possible. In addition, the movement through the electrolyte and the thorough mixing of the material as well as the transport through the electrolyte must be carried out in such a way that gentle treatment of the material is ensured and even delicate parts are not mechanically damaged during the electrodeposition.
These requirements, however, exist not only for electrolytic surface coating, in particular mass electroplating, but may occur for example also in electrochemical surface treatment of pourable material in liquids, as for example in chemical and electrolytic pickling in acids or bases, as well as in electrolytic degreasing in alkaline baths or also in electrolytic polishing. In electrolytic surface treatment the bulk material is connected either as cathode or as anode, connection as anode being employed for example in electrolytic polishing, while for example for the separation of aluminum the bulk material is preferably connected as cathode.
For mass electroplating, in particular for electrodeposition of aluminum, a known apparatus is suitable where for transporting the bulk material through the treatment bath a vibrator conveyor with a horizontal and a vertical oscillation component is provided. This vibrator conveyor transports the bulk material, utilizing the forces of gravity, in a spiral conveying trough in ascending direction around a supporting column connected with the conveying trough. The vibrator conveyor with the supporting column is lodged in a gasproof vessel containing an electrolyte into which the vibrator conveyor dips partially. As drive means serve for example oblique-action vibrators or obliquely set rods. Additionally, gravity conveyors in the form of a down pipe may be provided. Such vibrator conveyors require relatively little drive force and permit gentle conveyance of the bulk material. Intensive product movement and good electrolyte exchange as well as uniform current consumption over the entire effective surface of the spread-out material is obtained (DE-OS 35 24 510).
In such an apparatus, with the oscillating movement of the central pipe and of the conveying trough connected with it a portion of the liquid, e.g. the electrolyte, corresponding to the vibration amplitude must be displaced. This, however, becomes difficult in large installations when the outside diameter of the central pipe and hence the inside diameter of the conveying trough as well as its width and the height of the liquid column exceed predetermined values.